xl: add node-affinity to the output of `xl list`

xl: add node-affinity to the output of `xl list`

Node-affinity is now something that is under (some) control of the
user, so show it upon request as part of the output of `xl list'
by the `-n' option.

Re the patch, the print_bitmap() related hunk is _mostly_ code motion,
although there is a very minor change in the code, basically to allow
using the function for printing both cpu and node bitmaps (as, in case
all bits are sets, it used to print "any cpu", which doesn't fit the
nodemap case).

Signed-off-by: Dario Faggioli <dario.faggioli@citrix.com>
Acked-by: Juergen Gross <juergen.gross@ts.fujitsu.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>